JP2007333952A - Video display apparatus and head mount display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid degradation in the luminance and image quality of an observed video, due to adjustment of optical axes. <P>SOLUTION: Each of video display apparatuses 1R and 1L is provided with an optical axis adjustment means 15 for adjusting an angle formed by a pair of optical axes, right and left, by altering a relative positional relation between a video displayed on each display element 14 and an eyepiece optical system 21 in a direction intersecting the corresponding optical axis. At this time, each light source 11 is disposed so as to almost conjugate to an optical pupil E. Each optical axis adjustment means 15 alters the positional relation without altering the position of the optical pupil E relative to the eyepiece optical system 21. Thus, even if the apparatus is originally designed so that light intensity is high in the position of the optical pupil E determined in the design stage, the light intensity at the position of the pupil can be obtained even after the adjustment of the optical axis. Since the positions of the optical pupils E relative to the eyepiece optical systems 21 are not changed by the adjustment of the optical axes, video light can be guided to the optical pupils E by using portions of the eyepiece optical systems 21, which are designed to restrain aberrations. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image display device that provides an observer with an image displayed on a display element as a virtual image, and a head mounted display (hereinafter also referred to as an HMD) including the image display device.

  Conventionally, there has been proposed an HMD that allows an observer to observe an image displayed on a pair of left and right display elements with both eyes. When an observer wears such a binocular HMD, the observer superimposes the left and right display images and observes them as one image. At this time, if the positions of the optical axes of the left and right optical systems are shifted and the angle formed by the pair of left and right optical axes deviates from the reference, it is difficult for the observer to superimpose the respective display images.

  Therefore, for example, in the apparatus of Patent Document 1, the optical axis can be adjusted in a direction perpendicular to the direction in which both eyes are arranged (left-right direction) in at least one of the left and right optical systems. Here, FIG. 29 is an explanatory view schematically showing a schematic configuration of one of the left and right optical systems in the apparatus of Patent Document 1. In FIG. As shown in the figure, the optical axis can be adjusted in the vertical direction by integrally moving the light source 101 and the liquid crystal panel 102 in the vertical direction. In addition, the solid line in the figure shows the position and optical path of the light source 101 and the liquid crystal panel 102 before movement, and the broken line shows the position and optical path of the light source 101 and liquid crystal panel 102 after movement.

  Further, for example, in the apparatus of Patent Document 2, an adjustment mechanism that adjusts the distance between the eyepiece windows in accordance with the vergence of the observer at the bridge portion of the HMD, that is, the portion connecting the eyepiece windows arranged in front of both eyes. Is provided. Although it is possible to adjust the positional relationship between the left and right optical axes by this adjustment mechanism, the detailed configuration of the adjustment mechanism is not clear.

JP-A-8-240785 JP 2000-19450 A

  However, in the apparatus of Patent Document 1, since the positional relationship between the light source 101 and the optical pupil E is not defined at all, when the light source 101 and the liquid crystal panel 102 are moved with respect to the lens 103, as shown in FIG. The position of the optical pupil E with respect to the lens 103 is shifted. For this reason, the brightness of the observation image may be lowered, or a large aberration may occur, resulting in a decrease in the image quality of the observation image.

  That is, for example, when the light source 101 is configured as a point light source, or when a diffuser plate is disposed in the optical path, the optical pupil before optical axis adjustment is taken into account in consideration of the radiation characteristics of the light source 101 and the diffusion characteristics of the diffuser plate. Generally, the apparatus is designed so that the light intensity is increased at the position E. Therefore, as shown in FIG. 29, when the position of the optical pupil E with respect to the lens 103 is shifted due to the optical axis adjustment, the optical intensity at which the light reaches the optical position is reduced to a position lower than the position of the optical pupil E before the optical axis adjustment. As a result, the image observed at the position of the optical pupil E after the optical axis adjustment becomes dark.

  Further, when the position of the optical pupil E with respect to the lens 103 is shifted, a portion far from a portion designed to suppress the occurrence of aberration in the lens 103 is used (light is transmitted), and a large amount of aberration occurs. . For this reason, at the position of the optical pupil E after the optical axis adjustment, the image quality of the observation video is degraded.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a video display device capable of avoiding a decrease in luminance and image quality of an observation video due to optical axis adjustment, and the video display thereof. It is to provide a head mounted display including the device.

  An image display apparatus according to the present invention includes a pair of left and right light sources, a pair of left and right display elements that display light by modulating light from each light source, and a pair of left and right optical pupils that display image light displayed on each display element. By changing the relative positional relationship between the image displayed on the display element and the observation optical system in the direction intersecting the optical axis, with respect to at least one of the pair of left and right observation optical systems and left and right, respectively, An optical axis adjusting unit that adjusts an angle formed by the pair of optical axes, and the light source is disposed substantially conjugate with the optical pupil on each of the left and right sides, and the optical axis adjusting unit includes the optical pupil with respect to the observation optical system. It is characterized in that the positional relationship is changed without changing the position.

  According to the above configuration, in each of the left and right sides, the light emitted from the light source is modulated by the display element and guided as image light to the optical pupil via the observation optical system. Thereby, the observer can observe the display image with each eye by positioning the left and right eyes at the positions of the left and right optical pupils.

  Here, the optical axis adjusting means changes the relative positional relationship between the image displayed on the display element and the observation optical system in at least one of the left and right in the direction intersecting the optical axis, thereby making a pair of left and right light beams. Adjust the angle between the axes to adjust the optical axis. Note that the change in the positional relationship may be made by adjusting the position of the display element in the direction intersecting the optical axis, or the display position of the video displayed on the display element without adjusting the position of the display element. May be made by changing.

  At this time, in each of the left and right, the light source is arranged substantially conjugate with the optical pupil, and the optical axis adjusting means changes the positional relationship without changing the position of the optical pupil with respect to the observation optical system, and the optical axis. Adjustments can be made. By adjusting the optical axis by the optical axis adjusting means, for example, even when the apparatus is originally designed so that the light intensity is high at the position of the designed optical pupil, the light intensity at the optical pupil position is adjusted. It can be realized even after the optical axis is adjusted. Therefore, it is possible to avoid a decrease in luminance of the observation image at the optical pupil position due to the optical axis adjustment.

  Further, since the optical axis adjustment means adjusts the optical axis without changing the position of the optical pupil with respect to the observation optical system, for example, using a portion designed to suppress the occurrence of aberration in the observation optical system ( The image light from the display element can be guided to the optical pupil without using a portion away from the above portion as much as possible. Thereby, it is possible to suppress the occurrence of aberration due to the optical axis adjustment, and it is possible to avoid the deterioration of the image quality of the observation image due to the occurrence of the aberration.

  In the present invention, the optical axis adjusting means is configured to change the positional relationship by adjusting the position of the display element with respect to the observation optical system (changing in a direction crossing the optical axis). Also good.

  Even when the position of the display element is adjusted with respect to the observation optical system, the optical axis can be adjusted without changing the position of the optical pupil with respect to the observation optical system. Therefore, it is possible to avoid a decrease in luminance and image quality of the observation image due to the optical axis adjustment.

  The image display device of the present invention may further include a pair of left and right illumination optical systems that collect light from the light source and guide it to the display element.

  In this case, the light from the light source is collected by the illumination optical system and guided to the display element, so that the light use efficiency can be increased and a bright image can be provided to the observer. In addition, the distance between the light source and the display element can be shortened, and the apparatus can be reduced in size and weight.

  In the present invention, the light source is preferably an LED. The LED is inexpensive and small in size, and has a high emission purity because of its narrow emission wavelength width. Therefore, by configuring the light source with an LED, it is possible to realize an image display device that is inexpensive and small in size and has high color purity of the provided image.

  In the present invention, the light source may be configured to emit light having a plurality of wavelengths at which the light intensity reaches a peak. In this case, since the light source emits at least two colors of light, the light from the light source is modulated by the display element and guided to the observer's pupil through the observation optical system, so that the observer can see the color image. Can be observed.

  In the present invention, in each of the left and right, the observation optical system includes a volume phase type reflection type hologram optical element, and the hologram optical element diffracts and reflects the image light from the display element to form an optical pupil. The structure which guides may be sufficient.

  Volume phase type and reflection type hologram optical elements have high diffraction efficiency and a narrow half-value wavelength width of the diffraction efficiency peak. Therefore, by using such a hologram optical element and adopting a configuration in which image light from the display element is diffracted and reflected by the hologram optical element and guided to the optical pupil, a bright image with high color purity is provided to the observer. be able to. In particular, in the present invention, as described above, since the position of the optical pupil is not changed in the optical axis adjustment, the wavelength of the image light reaching the optical pupil does not change, and an image with high color reproducibility can be provided.

  The video display device of the present invention may further include a pair of left and right light source position adjusting mechanisms that change the position of the optical pupil by adjusting the position of the light source. In this case, for example, even when the optical pupil is formed at a position other than the position where the light having the desired wavelength arrives due to a manufacturing error, the light source position adjusting mechanism moves to the position where the light having the desired wavelength reaches. The optical pupil can be positioned, and the observer can observe an image of a desired color.

  In addition, in a configuration using a volume phase type and reflection type hologram optical element in which the half-value wavelength width of the diffraction efficiency peak is narrow, the light source can be moved, so the video color can be easily changed to the desired color by changing the wavelength of the video light. Can be changed. In addition, since the hologram optical element diffracts light of a specific wavelength incident at a specific incident angle, the incident angle and wavelength of light incident on the hologram optical element can be adjusted optimally by adjusting the position of the light source. Bright images can be provided. Further, the position of the optical pupil can be changed by moving the light source by the light source position adjusting mechanism regardless of the optical axis adjustment by the optical axis adjustment means (without changing the angle formed by the pair of left and right optical axes). Position adjustment can be easily performed.

  In the present invention, it is desirable that the hologram optical element has an axially asymmetric positive optical power. By using such a hologram optical element, the degree of freedom of arrangement of each optical member constituting the apparatus can be increased, and the apparatus can be easily downsized.

  In the present invention, it is desirable that the optical pupil is larger in the direction perpendicular to the incident surface than in the direction parallel to the incident surface of the optical axis to the hologram optical element. Note that the incident surface of the optical axis to the hologram optical element is a plane including the optical axis of incident light and the optical axis of reflected light in the hologram optical element.

  When the hologram optical element is axially asymmetric, the wavelength characteristic (wavelength selectivity) of the hologram optical element is large in the direction parallel to the incident surface of the optical axis to the hologram optical element, and the diffraction wavelength when the incident angle of incident light is deviated. It is easy to slip. Therefore, by enlarging the optical pupil in the direction perpendicular to the incident surface, that is, by enlarging the optical pupil in the direction where the wavelength characteristic is small, it is possible to provide an observer with an image that has less color unevenness and is easy to observe. Can do. In addition, the size of the optical pupil is relatively smaller in the direction parallel to the incident surface than in the direction perpendicular to the incident surface, so that the light from the light source is collected without waste and a bright image is provided to the observer. can do.

  In the present invention, it is desirable that the light source and the optical pupil are substantially conjugate in a direction parallel to the incident surface. In this case, it is possible to increase the light use efficiency of the light source and provide an image with high color reproducibility and color purity.

  In the present invention, the light source has (at least one set) three light emitting portions that emit light corresponding to the three primary colors, and each light emitting portion is arranged in a direction perpendicular to the incident surface. It is desirable to be arranged at.

  As described above, the direction perpendicular to the incident surface is a direction in which the wavelength characteristic of the hologram optical element is small. Therefore, by arranging the three light emitting sections that emit light of each color in a direction in which the wavelength characteristics of the hologram optical element are small, it is possible to mix colors in a direction in which the optical pupil can be enlarged, and a light source having three light emitting sections Even in the case of using, it is possible to provide an observer with a high-quality image with little color unevenness.

  In the present invention, the light source has an even number of three light-emitting portions that emit light corresponding to the three primary colors, and each light source in the direction perpendicular to the incident surface of the optical axis to the hologram optical element. It is desirable that the arrangement order of the light emitting units is reversed between adjacent groups.

  In this case, the center of gravity of the light intensity of each color of the emitted light from each light emitting unit (the sum of each set) is coincident (for example, located on the incident surface), so at the center of the optical pupil or in the vicinity thereof An image with little color unevenness can be provided to an observer. This configuration can be applied even when using a hologram optical element that does not have axially asymmetric positive optical power.

  In the present invention, the light source has an even number of three light-emitting portions, and each light-emitting portion is arranged in plane symmetry with respect to the incident surface and is perpendicular to the incident surface. It is desirable that the light emitting portions located at the same distance from the incident surface on both sides of the light emitting element emit light of the same color. In this case, the center of gravity of the light intensity of each color of the emitted light from each light emitting unit (added between each pair) matches on the incident surface, so that an image with little color unevenness at the center of the optical pupil can be viewed by the observer. Can be provided.

  In the present invention, the light source has two sets of three light emitting portions, and each light emitting portion of each set emits light from the incident surface side toward the outer side in the vertical direction with respect to the incident surface. It is desirable that they are arranged in an order that shortens the wavelength. In this case, with respect to light having a long wavelength, the difference in intensity due to the pupil position can be reduced, and an image with little color unevenness can be provided to the observer over the entire optical pupil.

  In the present invention, it is desirable that the hologram optical element is a combiner that guides image light and external light from the display element simultaneously to the observer's pupil. In this case, the observer can simultaneously observe the image provided from the display element and the external image via the hologram optical element.

  In the present invention, the half-value wavelength width of the diffraction efficiency peak of the hologram optical element is preferably 5 nm or more and 10 nm or less. Thus, since the half-value wavelength width of the diffraction efficiency peak of the hologram optical element is narrow, the observer can observe a bright image and the transmittance of external light is high, so that a bright external image can be observed. it can.

  In the present invention, the observation optical system first reflects the image light from the display element internally and guides it to the observer's pupil, while transmitting the external light to the observer's pupil. It is desirable to have By using such a first transparent substrate, the image from the display element can be observed, but the transmittance of external light is increased, so that a bright external image can be observed.

  In the present invention, it is desirable that the observation optical system has a second transparent substrate for canceling refraction of external light on the first transparent substrate. In this case, distortion can be prevented from occurring in the external image observed by the observer through the observation optical system.

  The head mounted display of the present invention includes the above-described video display device of the present invention and support means for supporting the video display device in front of the observer's eyes. According to this configuration, since the video display device is supported by the support means, the observer can observe the video provided from the video display device in a hands-free manner.

  According to the present invention, in each of the left and right sides, the light source is arranged substantially conjugate with the optical pupil, and the optical axis adjustment means can adjust the optical axis without changing the position of the optical pupil with respect to the observation optical system. It becomes. Thereby, the light intensity at the position of the designed optical pupil can be realized even after the optical axis adjustment, and a decrease in luminance of the observation image at the optical pupil position due to the optical axis adjustment can be avoided. In addition, since the image light from the display element can be guided to the optical pupil using a portion designed to suppress the occurrence of aberration in the observation optical system, aberration occurs due to optical axis adjustment. Therefore, it is possible to avoid the deterioration of the image quality of the observation image due to the occurrence of aberration.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings. First, in the present embodiment, the principle of optical axis adjustment in the video display device of the present invention will be mainly described.

  FIG. 1 is an explanatory diagram showing an expanded optical path of light emitted from the center of the display area of the display element 14 in the right-eye video display device 1R and the left-eye video display device 1L of the present embodiment. is there. FIG. 2 is an explanatory diagram showing the optical path of the light emitted from the light source 11 of the video display device 1R / 1L.

  The video display device 1 according to the present embodiment includes video display devices 1R and 1L that guide light of a display video to the right and left eyes of an observer, respectively. The video display devices 1R and 1L each include a light source 11, a condenser lens 13, a display element 14, an optical axis adjusting unit 15, and an eyepiece optical system 21. That is, the video display device 1 includes a light source 11, a condenser lens 13, a display element 14, an optical axis adjustment unit 15, and an eyepiece optical system 21 in a pair on the left and right.

  The light source 11 is composed of an LED that emits light of each wavelength of R (red), G (green), and B (blue), for example. The condenser lens 13 is an illumination optical system that condenses the light from the light source 11 and guides it to the display element 14. The display element 14 is a light modulation element that modulates the light from the light source 11 and displays an image, and is composed of, for example, a transmissive liquid crystal display element.

  The optical axis adjusting means 15 adjusts the angle formed by the pair of left and right optical axes by changing the relative positional relationship between the image displayed on the display element 14 and the eyepiece optical system 21. Hereinafter, the adjustment of the angle formed by the pair of left and right optical axes is referred to as optical axis adjustment. Here, the optical axis refers to an axis that optically connects the center of the display area of the display element 14 and the principal point of the eyepiece optical system 21. In the present embodiment, the optical axis adjusting means 15 positions the display element 14 with respect to the eyepiece optical system 21 in the direction intersecting the optical axis (including a direction perpendicular to the optical axis, a substantially perpendicular direction, and an oblique direction). By adjusting the position, the positional relationship is changed, and the optical axis is adjusted.

  More specifically, the optical axis adjusting means 15 has a holding portion 15 a that holds the display element 14. The holding portion 15a is slidable in a direction intersecting with the optical axis (here, substantially parallel to the display surface of the display element 14), and is finally fixed to a housing that accommodates the display element 14 and the like. The By adjusting the position of the display element 14 by sliding the holding portion 15a in this way, the relative positional relationship between the image displayed on the display element 14 and the eyepiece optical system 21 is changed in the direction intersecting the optical axis. Can be changed.

  The eyepiece optical system 21 is an observation optical system that guides the light of the image displayed on the display element 14 to the optical pupil E, and has optically positive power. Note that the eyepiece optical system 21 may have any of a hologram optical element, a half mirror, and a free-form surface prism instead of the lens.

  The light source 11 and the optical pupil E are arranged so as to be substantially conjugate by the condenser lens 13 and the eyepiece optical system 21. Therefore, if there is no member that changes the optical path, such as a diffusion plate, in the optical path, the image of the light source 11 is formed on the optical pupil E.

  In each of the video display devices 1R and 1L having the above-described configuration, the light emitted from the light source 11 is collected by the condenser lens 13 and guided to the display element 14. When the light that has entered the display element 14 passes through each pixel of the display element 14, the light is slightly diffused by the pixel and emitted as video light. Video light from the display element 14 is guided to the optical pupil E through the eyepiece optical system 21. The optical pupil E has a certain size as a result of the size of the light source 11 being enlarged by the image magnification of the optical system and a little larger due to the diffusion in the display element 14.

  The positional relationship between the light source 11 and the optical pupil E is substantially conjugate. However, the greater the degree of diffusion of light transmitted through the display element 14 at each pixel, the more the light source 11 and the optical pupil E are conjugate. In other words, the image of the light source 11 is not clearly formed on the optical pupil E. On the other hand, the smaller the diffusion, the closer to the conjugate, and the intensity distribution of the emitted light from the light source 11 is preserved.

  When the light source 11 and the optical pupil E are in a substantially conjugate positional relationship, the position of the display element 14 is adjusted by the optical axis adjusting unit 15 in a direction intersecting the optical axis, and the image displayed on the display element 14 and the eyepiece are displayed. By changing the relative positional relationship with the optical system 21, the optical axis can be adjusted without changing the position of the optical pupil E with respect to the eyepiece optical system 21. 1 and 2 show, for example, an optical path before shifting the position of the display element 14 of the video display device 1L in a direction intersecting the optical axis (solid line) and an optical path after being shifted (broken line). It can be seen that the position of the optical pupil E with respect to the optical system 21 does not change before and after the position of the display element 14 is shifted.

  As described above, the optical axis adjustment can be performed without changing the position of the optical pupil E with respect to the eyepiece optical system 21 by the optical axis adjustment means 15, so that the light intensity is adjusted at the position of the optical pupil E designed first. Even when the device is originally designed to be high, the light intensity at the position of the optical pupil E can be realized even after the optical axis adjustment. Therefore, it is possible to avoid a decrease in luminance of the observation image at the position of the optical pupil E due to the optical axis adjustment.

  Further, by adjusting the optical axis without changing the position of the optical pupil E with respect to the eyepiece optical system 21, use a portion far from the portion designed to suppress the occurrence of aberration in the eyepiece optical system 21. Instead, the image light from the display element 14 can be guided to the optical pupil E. In other words, the image light that has passed through the optical path in which the optical aberration is good in the eyepiece optical system 21 can be guided to the optical pupil E.

  1 and 2, the position where the image light from the display element 14 enters the eyepiece optical system 21 and the position where the light is emitted from the eyepiece optical system 21 are greatly different before and after the optical axis adjustment. This is illustrated in order to easily explain the principle of the present invention in which the optical axis is adjusted without changing the position of the optical pupil E with respect to the eyepiece optical system 21 by the movement of the display element 14. Actually, the change in the position of both due to the movement of the display element 14 may be considered as a minute amount before and after the optical axis adjustment.

  As described above, since the image light from the display element 14 can be guided to the optical pupil E by using the portion designed to suppress the occurrence of aberration in the eyepiece optical system 21, it is caused by the optical axis adjustment. As a result, it is possible to suppress the occurrence of aberration, and to avoid the deterioration of the image quality of the observation image due to the occurrence of the aberration.

  Further, since the light from the light source 11 is condensed by the condenser lens 13 and guided to the display element 14, the light use efficiency can be increased, and a bright image can be provided to the observer. Further, by disposing the condenser lens 13, the distance between the light source 11 and the display element 14 can be shortened, and the apparatus can be reduced in size and weight.

  In FIG. 1 and FIG. 2, the optical axis adjusting means 15 is provided in a pair on the left and right, but may be provided on at least one of the left and right.

  In this embodiment, the optical axis adjustment is performed by adjusting the position of the display element 14. However, the optical axis adjustment may be performed by changing the display position of the image displayed on the display element 14 within the display surface. At this time, if the display element 14 has an image display area wider than the display image before the optical axis adjustment, all the images to be displayed can be displayed even after the optical axis adjustment (after the display position is moved). .

  By the way, although the example which has arrange | positioned the light source 11 so that the light radiate | emitted from the light source 11 (light emitted from one point of LED) may pass through the display element 14 as divergent light was demonstrated above, a display element was demonstrated. The light source 11 may be arranged so as to be convergent light when passing through 14.

  3 shows the optical path of light emitted from the center of the display area of the display element 14 in the video display devices 1R and 1L in which the distance between the light source 11 and the principal point of the condenser lens 13 is wider than in the case of FIG. It is explanatory drawing developed and shown. FIG. 4 is an explanatory diagram showing the optical path of light emitted from the light source 11 of the video display device 1R / 1L having the configuration shown in FIG. In these drawings, the solid line indicates the optical path before the optical axis adjustment, and the broken line indicates the optical path after the optical axis adjustment.

  In this configuration, the light source 11 is disposed at a position farther from the focal position of the condenser lens 13. Even in this case, the position of the optical pupil E with respect to the eyepiece optical system 21 by the optical axis adjusting means 15. The optical axis can be adjusted without changing the. Therefore, as in the case of the configuration of FIGS. 1 and 2, it is possible to avoid a decrease in image brightness and a decrease in image quality due to optical axis adjustment.

  The distance between the light source 11 and the principal point of the condenser lens 13 is the same as in the case of FIGS. 1 and 2, and by using the condenser lens 13 with high power, the image light from the display element 14 is converted into convergent light. It is good also as composition to do.

  Further, the constituent members may be arranged so that the light emitted from the light source 11 becomes parallel light when passing through the display element 14. FIG. 5 is an explanatory diagram showing the optical path of light emitted from the center of the display area of the display element 14 in the video display devices 1R and 1L in which the light source 11 is arranged at the focal position of the condenser lens 13. FIG. FIG. 6 is an explanatory diagram showing the optical path of the light emitted from the light source 11 of the video display device 1R / 1L configured as shown in FIG. In these drawings, the solid line indicates the optical path before the optical axis adjustment, and the broken line indicates the optical path after the optical axis adjustment.

  When the display element 14 is illuminated with parallel light, the light source 11 and the condenser lens 13 are formed integrally with the display element 14 and moved in a direction intersecting the optical axis with respect to the eyepiece optical system 21. The optical axis can be adjusted without changing the position of the optical pupil E with respect to the eyepiece optical system 21. Accordingly, even in this case, it is possible to avoid a decrease in image luminance and a decrease in image quality due to the optical axis adjustment.

  The optical axis can be adjusted without changing the position of the optical pupil E with respect to the eyepiece optical system 21 by moving only the display element 14 in the direction intersecting the optical axis. As described above, in the configuration in which the light source 11 and the condenser lens 13 are formed integrally with the display element 14 and moved together, the degree of freedom in optical design is limited. It is preferable to adjust the optical axis by moving only the element 14.

  7 shows an optical path of light emitted from the center of the display area of the display element 14 in the image display devices 1R and 1L in which the light source 11 directly illuminates the display element 14 without providing the condenser lens 13. It is explanatory drawing which expands and shows. FIG. 8 is an explanatory diagram showing the optical path of light emitted from the light source 11 of the video display device 1R / 1L configured as shown in FIG. In these drawings, the solid line indicates the optical path before the optical axis adjustment, and the broken line indicates the optical path after the optical axis adjustment.

  In this configuration, the condensing lens 13 is not provided in the optical path as in FIGS. 1 to 6, so that the apparatus can be configured at low cost. Further, since the light from the light source 11 is not condensed by the condenser lens 13, the observed image is slightly darker than that of the configuration shown in FIGS. 1 to 6, and the light source 11 and the optical pupil E are substantially conjugate. In order to arrange, the space | interval of the light source 11 and the display element 14 becomes long, and an apparatus becomes a little large. However, the optical axis can be adjusted without changing the position of the optical pupil E with respect to the eyepiece optical system 21 by moving the display element 14 in the direction intersecting the optical axis with respect to the eyepiece optical system 21. There is no change. Therefore, even with the configurations of FIGS. 7 and 8, it is possible to avoid a decrease in image luminance and a decrease in image quality due to optical axis adjustment.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. For the convenience of explanation, the same members as those in the first embodiment are denoted by the same member numbers. The points that are not mentioned in the first embodiment will be appropriately described. The video display device 1 of the present embodiment has the same basic configuration as that of the first embodiment, and is a more specific embodiment of this.

(1. Configuration of video display device)
FIG. 9 is a cross-sectional view showing a schematic configuration of the video display device 1 (1R · 1L), and FIG. 10 is an explanatory diagram showing an optical path in the video display device 1 optically developed in one direction. The video display device 1 includes a light source 11, a unidirectional diffuser plate 12, a condenser lens 13, a display element 14, an optical axis adjusting unit 15, and an eyepiece optical system 21. As shown in FIG. 9, the light source 11, the unidirectional diffuser plate 12, the condenser lens 13, and the display element 14 are accommodated in the housing 10, and a part of the eyepiece optical system 21 (of an eyepiece prism 22 described later). Is located in the housing 10.

  Here, for convenience of explanation below, directions are defined as follows. First, the optical axis is an axis that optically connects the center of the display area of the display element 14 and the center of the optical pupil E at the time of design formed by the eyepiece optical system 21 (in the second embodiment, the optical axis is asymmetrical). Since the system is used and the principal point is not clear, the definition of the optical axis is changed). The optical axis direction when the optical path from the light source 11 to the optical pupil E is developed is taken as the Z direction. In addition, a direction perpendicular to an incident surface of an optical axis to a hologram optical element 24 to be described later of the eyepiece optical system 21 is an X direction, and a direction perpendicular to the ZX plane is a Y direction. The plane of incidence of the optical axis on the hologram optical element 24 is a plane including the optical axis of light incident on the hologram optical element 24 and the optical axis of light reflected by the hologram optical element 24, that is, the YZ plane. Point to. Hereinafter, the incident surface is simply referred to as an incident surface or an optical axis incident surface.

  In the present embodiment, the light source 11 includes three light emitting chips that emit light having wavelengths corresponding to the three primary colors of red (R), green (G), and blue (B) as light emitting units 11R, 11G, and 11B (FIG. 10). (See, for example, Nichia Chemical). Each light emission part 11R * 11G * 11B is located in a line with the X direction which is a direction with the large spreading | diffusion by the one way diffusion plate 12 (refer FIG. 10). Thereby, the intensity unevenness of each color on the optical pupil E is reduced, and the color unevenness can be reduced.

  The LED is inexpensive and small in size, and has a high color purity because the emission wavelength width is narrow as will be described later. Therefore, by configuring the light source 11 with LEDs, an inexpensive and small image display device can be realized, and the color purity of the image provided to the observer can be increased.

  The unidirectional diffuser plate 12 diffuses light emitted from the light source 11, but the degree of diffusion varies depending on the direction. More specifically, the unidirectional diffuser 12 diffuses incident light in the X direction by about 40 ° and diffuses incident light in the Y direction by about 0.5 °. The unidirectional diffuser plate 12 has an optically flat surface on the light source 11 side and an uneven surface that diffuses the surface on the condenser lens 13 side by unevenness. Therefore, the divergent light from the light source 11 is refracted by the flat surface of the unidirectional diffusion plate 12 and diffused in a slightly condensed state, so that the condensing state is slightly preserved. Therefore, the unidirectional diffuser plate 12 has a function of a convex lens, and the incident light on the unidirectional diffuser plate 12 is slightly refracted in the direction necessary for forming the optical pupil E.

  The condenser lens 13 is an illumination optical system that condenses the light from the light source 11 and guides it to the display element 14. The condensing lens 13 is composed of a cylinder lens that condenses the light diffused by the unidirectional diffusion plate 12 in the Y direction, and is arranged so that the diffused light efficiently forms the optical pupil E. Yes. In this embodiment, the optical pupil E has a size in the X direction of 6 mm and a size in the Y direction of 2 mm. Thus, the optical pupil E has a size of 6 mm, which is larger than the human pupil (about 3 mm) in one direction (X direction), so that the observer can easily observe the image. On the other hand, since the optical pupil E has a size of 2 mm which is smaller than the human pupil in the other direction (Y direction), the light from the light source 11 is condensed on the optical pupil E in the above direction without waste. Thereby, the observer can observe a bright image.

  The display element 14 displays an image by modulating the light emitted from the light source 11 in accordance with image data, and is configured by a transmissive liquid crystal display element having pixels in a matrix in which light is transmitted. Has been. Each pixel of the display element 14 is provided with a color filter (transmission wavelength limiting filter) that limits transmission of light emitted from the light source 11 according to the wavelength of the light. The color filter includes three types of filters corresponding to the three primary colors, and each of the filters transmits light having a wavelength corresponding to the three primary colors of RGB among the light emitted from the light source 11, while the remaining light. Limit transmission of light.

  Thus, the display element 14 has a color filter, and the display element 14 displays a color image by modulating the light from the light source 11 according to the image data and emitting it through the color filter. Is possible. The display element 14 is arranged such that the long side direction of the rectangular display region is the X direction and the short side direction is the Y direction.

  The eyepiece optical system 21 is an observation optical system that guides light of an image displayed on the display element 14 to an observer's pupil (or optical pupil E), and an eyepiece prism 22 (first transparent substrate), a deflection prism, and the like. 23 (second transparent substrate) and a hologram optical element 24.

  The eyepiece prism 22 totally reflects the image light from the display element 14 and guides it to the observer's pupil through the hologram optical element 24, while allowing the external light to pass through and guide it to the observer's pupil. Along with the deflection prism 23, it is made of, for example, an acrylic resin. The eyepiece prism 22 is formed in a shape in which the lower end portion of the parallel plate is made thinner and wedged as it approaches the lower end, and the upper end portion thereof becomes thicker as it approaches the upper end. Further, the eyepiece prism 22 is bonded to the deflection prism 23 with an adhesive so as to sandwich the hologram optical element 24 disposed at the lower end thereof.

  The deflection prism 23 is configured by a substantially U-shaped parallel plate in plan view, and is integrated with the eyepiece prism 22 when bonded to the lower end portion and both side surface portions (left and right end surfaces) of the eyepiece prism 22. It becomes a substantially parallel plate. By joining this deflecting prism 23 to the eyepiece prism 22, it is possible to prevent distortion in the external image observed by the observer via the eyepiece optical system 21.

  That is, for example, when the deflection prism 23 is not joined to the eyepiece prism 22, the external light is refracted when passing through the wedge-shaped lower end portion of the eyepiece prism 22, so that the external image observed through the eyepiece prism 22 is distorted. Arise. However, the deflection prism 23 is joined to the eyepiece prism 22 to form an integral substantially parallel plate, so that the deflection when the external light passes through the wedge-shaped lower end of the eyepiece prism 22 is canceled by the deflection prism 23. Can do. As a result, it is possible to prevent distortion in the external image observed through the see-through.

  Each surface (light incident surface, light exit surface) of the eyepiece prism 22 and the deflection prism 23 may be a flat surface or a spherical surface. If each surface of the eyepiece prism 22 and the deflecting prism 23 is a curved surface, the eyepiece optical system 21 can have a function as a correction spectacle lens.

  The hologram optical element 24 diffracts image light (wavelength light corresponding to the three primary colors) emitted from the display element 14 and enlarges the image displayed on the display element 14 to guide it to the observer's pupil as a virtual image. It is a volume phase reflection hologram and has positive optical power that is axially asymmetric. That is, the hologram optical element 24 has the same function as an aspherical concave mirror having positive power. Thereby, the degree of freedom of arrangement of each optical member constituting the apparatus can be increased, and the apparatus can be easily reduced in size, and an image with good aberration correction can be provided to the observer. Further, the hologram optical element 24 functions as a combiner that simultaneously guides the image light from the display element 14 and external light to the observer's pupil, and the observer can connect the display element 14 via the hologram optical element 24. The provided image and the external image can be observed simultaneously. A method for producing the hologram optical element 24 in the present embodiment will be described later.

(2. Operation of video display device)
Next, the operation of the video display device 1 having the above configuration will be described. The light emitted from the light source 11 is diffused by the unidirectional diffusion plate 12, condensed by the condenser lens 13, and enters the display element 14. The light incident on the display element 14 is modulated for each pixel based on the image data, and is emitted as video light through the color filter. That is, a color image is displayed on the display element 14.

  The image light from the display element 14 enters the eyepiece prism 22 of the eyepiece optical system 21 from its upper end surface, is totally reflected a plurality of times by two opposing surfaces, and enters the hologram optical element 24. The light incident on the hologram optical element 24 is diffracted and reflected there and reaches the optical pupil E. At the position of the optical pupil E, the observer can observe an enlarged virtual image of the image displayed on the display element 14.

  On the other hand, the eyepiece prism 22 and the deflecting prism 23 transmit almost all the external light, so that the observer can observe the external image. Therefore, the virtual image of the image displayed on the display element 14 is observed while being overlapped with a part of the external image.

  As described above, in the video display device 1, since the video light emitted from the display element 14 is guided to the hologram optical element 24 by total reflection in the eyepiece prism 22, as in the case of a normal spectacle lens, The thickness of the eyepiece prism 22 and the deflection prism 23 can be about 3 mm, and the video display device 1 can be reduced in size and weight. Further, by using the eyepiece prism 22 that totally reflects the image light from the display element 14, a high external light transmittance can be secured and a bright external image can be provided to the observer.

(3. Optical axis adjustment)
Also in the present embodiment, as in the first embodiment, the optical axis adjusting unit 15 adjusts the position of the display element 14 with respect to the eyepiece optical system 21 in the direction intersecting the optical axis, thereby changing the display element 14 to the display element 14. The relative positional relationship between the displayed image and the eyepiece optical system 21 is changed. For this reason, the optical axis adjusting means 15 has a holding portion 15 a that holds the display element 14. The holding portion 15a is slidable in a direction intersecting the optical axis (here, substantially parallel to the display surface (XY plane) of the display element 14) while holding the display element 14.

  Also in the present embodiment, as in the first embodiment, the light source 11 is disposed so as to be substantially conjugate with the optical pupil E by the condenser lens 13 and the eyepiece optical system 21. Therefore, the position of the optical pupil E with respect to the eyepiece optical system 21 is changed by adjusting the position of the display element 14 by sliding the holding unit 15a in the above direction, for example, Δy, and fixing the holding unit 15a to the housing 10. The optical axis can be adjusted without any problems. As a result, as in the first embodiment, it is possible to avoid a decrease in image luminance and a decrease in image quality due to optical axis adjustment.

  In particular, in the present embodiment, the unidirectional diffuser 12 is used, and in consideration of both the radiation characteristics of the light source 11 and the diffusive characteristics of the unidirectional diffuser 12, the optical pupil E before the optical axis adjustment is positioned. The optical design is such that the light intensity is high. Here, FIG. 11 is a graph showing the radiation characteristics (relationship between radiation angle and luminous intensity) of the RGB LEDs constituting the light source 11, and FIG. 12 shows the diffusion characteristics (emission angle and light) of the unidirectional diffusion plate 12. It is a graph which shows a relationship with an intensity | strength. FIG. 13 is an explanatory diagram showing the light intensity distribution (luminance distribution) of a certain wavelength (for example, R light) at the position of the optical pupil E before the optical axis adjustment.

  In this way, the image display device 1 is designed so that the light intensity becomes high at the position of the optical pupil E before the optical axis adjustment in consideration of the radiation characteristics of the light source 11 and the diffusion characteristics of the unidirectional diffusion plate 12. Even in this case, the optical axis adjustment means 15 can perform the optical axis adjustment without changing the position of the optical pupil E with respect to the eyepiece optical system 21, so that the optical pupil E set so that the light intensity is increased. The light intensity at the position can be realized even after adjusting the optical axis. Therefore, it is possible to avoid a decrease in luminance of the observation image at the position of the optical pupil E due to the optical axis adjustment.

(4. Method for manufacturing hologram optical element)
Next, a method for manufacturing the hologram optical element 24 of the present embodiment will be briefly described as follows. FIG. 14 is a cross-sectional view showing a schematic configuration of an optical system used for manufacturing the hologram optical element 24.

  First, the hologram photosensitive material 24a is applied to the surface of the eyepiece prism 22 to which the deflection prism 23 is bonded. Here, it is assumed that the hologram photosensitive material 24a is applied on the eyepiece prism 22 over a wider range than the irradiation range of the two light beams used in production. Then, the eyepiece prism 22 coated with the hologram photosensitive material 24a is arranged at a predetermined position of the optical system shown in FIG.

  In the optical system, laser light from a light source (not shown) is split into two light beams and converted into point light sources 31 and 41 that emit three colors of RGB, respectively. Light emitted from the point light source 31 (one of the two produced light beams) is irradiated to the hologram photosensitive material 24a from the back side (the eyepiece prism 22 side) through the diaphragm 32. In addition, the irradiation range of the emitted light with respect to the hologram photosensitive material 24a is a range in which only the central light beam having good optical performance is diffracted among the light irradiated at the time of reproducing the produced hologram optical element 24.

  On the other hand, light emitted from the point light source 41 is irradiated from the surface side (opposite side to the eyepiece prism 22) onto the hologram photosensitive material 24a through the manufacturing optical system 42, the stop 43, and the reflection mirror 44 in this order. By irradiating the hologram light-sensitive material 24a with the emitted light through the manufacturing optical system 42, the hologram optical element 24 to be formed can have an axially asymmetric positive power. In addition, the irradiation range of the emitted light with respect to the hologram photosensitive material 24a is a range in which only the central light beam having good optical performance is diffracted among the light irradiated at the time of reproducing the produced hologram optical element 24.

  By irradiation with these two light beams, interference fringes are recorded in the overlapping portion of the irradiation range of the two light beams on the hologram photosensitive material 24a, and the hologram optical element 24 is manufactured. Thereafter, baking processing and fixing processing are performed, and the eyepiece prism 22 on which the hologram optical element 24 is formed and the deflection prism 23 (see FIG. 9) are bonded together to complete the eyepiece optical system 21.

  In the optical system described above, the apertures 32 and 43 limit the numerical aperture of the point light sources 31 and 41 (the diameter of the emitted light beam), so that the two light beams produced on the hologram photosensitive material 24a can have the same size. In addition, the hologram optical element 24 can be produced only in a range in which the central light beam having a good optical performance is irradiated among the light irradiated when reproducing the hologram optical element 24. Further, since the two produced light beams interfere with each other in the same range, interference with only one laser beam hardly occurs, and unnecessary interference fringes are not recorded on the hologram photosensitive material 24a. Therefore, the hologram optical element 24 having optically good performance that hardly generates flare and ghost can be produced, and a high-quality image can be provided to the observer.

  Further, since the two light beams used at the time of manufacture are formed by restricting the divergence angle of the light emitted from the corresponding point light sources 31 and 41 with the diaphragms 32 and 43, the hologram optical element on the eyepiece prism 22 is formed. The size of 24 can be easily and reliably controlled at low cost.

  The point light source 31 is disposed in the vicinity of the optical pupil E. As described above, by substantially matching the position of the point light source 31 and the position of the optical pupil E when the hologram optical element 24 is manufactured, the video display color can be made the same regardless of the position of the screen. Further, the wavelength of light that is diffracted by the hologram optical element 24 and reaches the optical pupil E during reproduction differs depending on the position of the optical pupil E. However, in the present embodiment, the optical axis adjustment unit 15 performs the optical axis adjustment without changing the position of the optical pupil E with respect to the eyepiece optical system 21, so that the wavelength of light reaching the optical pupil E changes due to the optical axis adjustment. Therefore, the color reproducibility can be kept good.

  Conversely, if the position of the optical pupil E is adjusted, the wavelength of light reaching the optical pupil E can be adjusted. This will be described later.

(5. Effects that can expand the color reproduction range)
In the present embodiment, the color reproduction region of the display image (virtual image) of the image display device 1 can be expanded by appropriately setting the characteristics of the light source 11 and the hologram optical element 24. Hereinafter, this point will be described.

  FIG. 15 is an explanatory diagram showing the spectral intensity characteristics of the light source 11, that is, the relationship between the wavelength of the emitted light and the light intensity. The light source 11 is, for example, an RGB integrated LED (for example, Nichia Chemical) that emits light in three wavelength bands of 462 ± 12 nm, 525 ± 17 nm, and 635 ± 11 nm with a peak wavelength of light intensity and a wavelength width of half value of light intensity. Made). Here, the peak wavelength of light intensity is the wavelength at which the light intensity reaches a peak, and the wavelength width at half value of the light intensity is the wavelength width at which the light intensity is at half value of the light intensity peak. It is. The light intensity in FIG. 15 is shown as a relative value when the maximum light intensity of B light is 100.

That is, in this embodiment, when the peak wavelengths of the BGR light intensity in the light source 11 are λ1 _B , λ1 _G , and λ1 _R , respectively, λ1 _B = 462 nm, λ1 _G = 525 nm, and λ1 _R = 635 nm. . Further, assuming that the wavelength widths of the BGR light intensity at the light source 11 are Δλ1 _B , Δλ1 _G , and Δλ1 _R , respectively, Δλ1 _B = 24 nm, Δλ1 _G = 34 nm, and Δλ1 _R = 22 nm.

  The RGB light intensity of the light source 11 is adjusted in consideration of the diffraction efficiency of the hologram optical element 24 and the light transmittance of the display element 14, thereby enabling white display.

  In this way, the light source 11 emits light having a plurality of wavelengths at which the light intensity reaches a peak. Therefore, the light from the light source 11 is modulated by the display element 14, and the observer's pupil is obtained via the eyepiece optical system 21. Thus, the observer can observe a color image.

  On the other hand, FIG. 16 is an explanatory diagram showing the wavelength dependence of the diffraction efficiency in the hologram optical element 24. As shown in the figure, the hologram optical element 24 has, for example, 465 ± 5 nm (B light), 521 ± 5 nm (G light), and 634 ± 5 nm (R light) at the peak wavelength of diffraction efficiency and the half width of the diffraction efficiency. ) Is diffracted (reflected) in the three wavelength regions. Here, the peak wavelength of diffraction efficiency is the wavelength at which the diffraction efficiency reaches a peak, and the wavelength width at half maximum of the diffraction efficiency is the wavelength width at which the diffraction efficiency is at half the peak of the diffraction efficiency. It is. The diffraction efficiency in FIG. 16 is shown as a relative value when the maximum diffraction efficiency of B light is 100.

That is, in the hologram optical element 24 of the present embodiment, the peak wavelength λ2 _B of the diffraction efficiency of B light is 465 nm, the peak wavelength λ2 _G of the diffraction efficiency of G light is 521 nm, and the peak wavelength of the diffraction efficiency of R light is 521 nm. λ2 _R is 634 nm. Further, in the hologram optical element 24, the wavelength width Δλ2 _{B of the} half diffraction efficiency of B light is 10 nm, the wavelength width Δλ2 _{G of the} half diffraction efficiency of G light is 10 nm, and the wavelength width Δλ2 of the half diffraction efficiency of R light. _R is 10 nm.

  Since the hologram optical element 24 is fabricated so as to diffract only light having a specific wavelength at a specific incident angle, it hardly affects the transmission of external light. Therefore, the observer can see the external image as usual through the eyepiece prism 22, the hologram optical element 24 and the deflection prism 23. In addition, since the half-value wavelength width Δλ2 of the diffraction efficiency peak of the hologram optical element 24 is as narrow as 10 nm, the observer can observe a bright image and the transmittance of external light is high, so that a bright external image is observed. can do. Such an effect can be obtained if Δλ2 is 5 nm or more and 10 nm or less for each of RGB colors.

In this embodiment, the wavelength width Δλ1 (Δλ1 _B , Δλ1 _G , Δλ1 _R ) of the light intensity half value of BGR in the light source 11 is as wide as 20 nm or more, so that the wavelength of the diffraction efficiency half value for each color of BGR in the hologram optical element 24 By making the width Δλ2 (Δλ2 _B , Δλ2 _G , Δλ2 _R ) less than 20 nm (Δλ1> Δλ2), the color purity of BGR can be increased, and the color reproduction region of the observation image can be expanded.

  Here, FIG. 17 shows a color reproduction region of a virtual image represented using XY chromaticity coordinates in the XYZ color system. In the figure, a solid line A1 indicates the image display device 1 of the present embodiment, that is, the display element 14 having a color filter, the hologram optical element 24, and the light source 11 composed of RGB-integrated 3-in-1 LEDs. 2 shows a color reproduction region in a video display device having An alternate long and short dash line A2 indicates a color reproduction region in an image display apparatus having a display element 14 having a color filter, a hologram optical element 24, and a white light source (white LED). The video display device is also a video display device according to a fourth embodiment described later.

  On the other hand, a broken line A3 indicates a color in an image display device having a display element 14 having a color filter, an eyepiece optical system that does not use the hologram optical element 24, and a light source 11 composed of RGB-integrated 3-in-1 LEDs. The reproduction area is shown. An alternate long and two short dashes line A4 indicates a color reproduction region in a video display device having a display element 14 having a color filter, an eyepiece optical system not using the hologram optical element 24, and a white light source (white LED). An example of an eyepiece optical system that does not use the hologram optical element 24 is a free-form surface prism.

  From the figure, the color reproduction region is wider in the solid line A1 and the alternate long and short dash line A2 than in the broken line A3 and the two-dot chain line A4. From this, it can be said that by using the hologram optical element 24 whose diffraction efficiency half-value wavelength width Δλ2 is about 10 mm, the color purity can be increased and the color reproduction region can be expanded. In particular, as shown by the solid line A1, by using an RGB integrated type as the light source 11, the color reproduction region can be expanded as compared with the case where the light source 11 is configured with a white light source.

(6. Effect of reducing color unevenness)
By the way, in this embodiment, as described above, the optical pupil E is set to have a half intensity value of 6 mm in the X direction and 2 mm in the Y direction. That is, the optical pupil E is larger in the X direction, that is, the direction perpendicular to the incident surface than in the Y direction, that is, the direction parallel to the incident surface (YZ plane) of the optical axis to the hologram optical element 24. By setting the size of the optical pupil E in this way, the observer can observe a high-quality image with little color unevenness without being greatly affected by the wavelength characteristics (wavelength selectivity) of the hologram optical element 24. Can do. The reason is as follows.

  First, the relationship between the incident angle and the wavelength selectivity in the hologram optical element 24 will be described. In the hologram optical element 24 having interference fringes that diffract light having an incident angle greater than 0 degrees, the wavelength selectivity is smaller in the direction perpendicular to the incident surface than in the direction parallel to the incident surface (diffraction due to deviation of the incident angle). The wavelength shift is small. In other words, the angle selectivity with respect to the shift of the incident angle to the interference fringes is lower in the direction perpendicular to the incident surface than in the direction parallel to the incident surface. This is because, when light is incident on the interference fringes of the hologram optical element 24 with an incident angle, the angle deviation of the incident angle in the incident surface (YZ plane) becomes the angle deviation of the incident angle as it is. Although the influence on the wavelength is large, the angle shift in the direction perpendicular to the incident surface is small as the shift of the incident angle, and the influence on the diffraction wavelength is small.

  Therefore, when light having an angle shifted from the predetermined incident angle is incident on the interference fringes of the hologram optical element 24, the angle shift in the direction parallel to the incident surface is the angle in the direction perpendicular to the incident surface even with the same angle shift. The diffraction wavelength is greatly shifted from the shift (that is, the direction parallel to the incident surface has a high wavelength selectivity).

  Here, FIG. 18 is an explanatory diagram showing the relationship between the pupil position in the optical pupil E and the main diffraction wavelength (for example, R light) in the present embodiment. In the figure, a broken line B1 indicates a change in the diffraction wavelength of the optical pupil E in the X direction, and a solid line B2 indicates a change in the diffraction wavelength of the optical pupil E in the Y direction pupil. As described above, the change in the diffraction wavelength is larger in the Y direction parallel to the incident surface than in the X direction perpendicular to the incident surface.

  Therefore, by forming the optical pupil E small in the Y direction where the change in the diffraction wavelength is large, the range of change in the diffraction wavelength is narrowed, so that color unevenness on the optical pupil E can be reduced. Moreover, even if the optical pupil E is formed large in the direction perpendicular to the incident surface, an image with high color purity can be provided to the observer.

  In addition, although the incident surface of the light outside the optical axis incident surface is not slightly parallel to the optical axis incident surface, as described above, since the angle shift in the direction perpendicular to the incident surface has little influence on the diffraction wavelength, the optical axis incident surface The color unevenness does not increase even if the standard is used.

  Further, since the light source 11 is diffused by the unidirectional diffusion plate 12 in the X direction perpendicular to the optical axis incident surface, it is not conjugate with the optical pupil E, but in the Y direction parallel to the optical axis incident surface, It is substantially conjugate with the optical pupil E. Thereby, it is possible to increase the light use efficiency of the light source 11 and provide an image with high color reproducibility.

  Further, as described above, the three light emitting portions 11R, 11G, and 11B of the light source 11 are arranged in the X direction, which is a direction in which the unidirectional diffusion plate 12 has a large diffusion. It means that the two light emitting portions 11R, 11G, and 11B are arranged in a direction perpendicular to the incident surface of the optical axis. The direction perpendicular to the incident surface is a direction in which the wavelength selectivity in the hologram optical element 24 is small, so that the optical pupil E can be enlarged by arranging the three light emitting units 11R, 11G, and 11B in the X direction. Even when the light source 11 that emits three colors of RGB is used, a high-quality image with little color unevenness can be provided to the observer.

  Further, since the wavelength selectivity of the hologram optical element 24 is high in the direction parallel to the incident surface, the color reproduction region changes greatly due to the positional deviation of the optical pupil E in the direction parallel to the incident surface. However, in this embodiment, even if the optical axis adjustment is performed, the position of the optical pupil E is not changed, so there is no change in the color reproduction region due to the optical axis adjustment. That is, the effect that there is no change in the color reproduction region due to the optical axis adjustment is greater in the direction parallel to the incident surface (the direction with high wavelength selectivity) than in the direction perpendicular to the incident surface.

(7. Adjustment of pupil position by adjusting light source position)
Next, adjustment of the position of the optical pupil E by adjusting the position of the light source 11 will be described.
FIG. 19 shows another configuration example of the video display device 1 of the present embodiment, and develops and shows an optical path of light emitted from the center of the display area of the display element 14 in each of the video display devices 1R and 1L. It is explanatory drawing. FIG. 20 is an explanatory diagram showing a developed optical path of light emitted from the light source 11 of the video display device 1R / 1L having the above-described configuration.

  The video display devices 1R and 1L further include a light source position adjusting mechanism 16. The light source position adjusting mechanism 16 changes the position of the optical pupil E by adjusting the position of the light source 11 (in a direction intersecting the optical axis), and has a holding portion 16 a that holds the light source 11. Yes. The holding portion 16a is slidable in a direction intersecting the optical axis while holding the light source 11. Therefore, by sliding the holding portion 16a in the above-mentioned direction, adjusting the position of the light source 11, and fixing the light source 11 to the casing 10 (see FIG. 9) at a predetermined position, as shown in FIGS. It is possible to adjust the position of the optical pupil E in a direction intersecting the optical axis without changing the angle formed by the pair of optical axes.

  In this way, the position of the optical pupil E can be changed by the light source position adjusting mechanism 16 regardless of the optical axis adjustment by the optical axis adjusting means 15 (without changing the angle formed by the pair of left and right optical axes). Therefore, even when the optical pupil E is formed at a position other than the position where light of a desired wavelength arrives due to, for example, a manufacturing error of the light source 11 or the hologram optical element 24 or a mechanical error (design error) of the apparatus. The optical pupil E can be positioned at a position where light of a desired wavelength reaches without breaking the positional relationship between the pair of left and right optical axes (while keeping the angle formed by the pair of optical axes constant). Therefore, even when the position of the optical pupil E is deviated due to a manufacturing error or the like, the observer can surely observe a video of a desired color by moving the pupil position by adjusting the position of the light source 11.

  In particular, since the position adjustment of the light source 11 and the optical axis adjustment do not affect each other, it is easy to adjust the pupil position, and the accuracy of the optical member and the design accuracy of the apparatus need not be so high. Therefore, the video display device 1 can be realized at low cost.

  Further, as described above, since the wavelength selectivity of the hologram optical element 24 is high in the direction parallel to the optical axis incident surface, the change of the position of the optical pupil E in the above direction changes the image light guided to the optical pupil E. The wavelength can be easily changed, and an image with high color reproducibility can be provided to the observer. Even in the direction perpendicular to the optical axis incident surface, the wavelength selectivity of the hologram optical element 24 is not large, but the wavelength change due to the change of the position of the optical pupil E is small.

  Further, since the hologram optical element 24 diffracts light having a specific wavelength incident at a specific incident angle, the incident angle and wavelength of light incident on the hologram optical element 24 are optimized by adjusting the position of the light source 11. Can be adjusted to provide a bright image.

  Here, the light source position adjustment mechanism 16 moves only the light source 11 in the direction intersecting the optical axis to adjust the position of the optical pupil E. However, the condenser lens 13 is moved in the direction intersecting the optical axis. It is good also as a structure which adjusts the position of the optical pupil E by moving. However, in this case, since the condenser lens 13 moves with respect to the display range of the display element 14, the condenser lens 13 needs to be set slightly larger.

[Embodiment 3]
The following will describe still another embodiment of the present invention with reference to the drawings. In addition, the same member number is attached to the same structure as Embodiment 1 or 2, and the description is abbreviate | omitted.

  FIG. 21 is an explanatory diagram showing the optical path in the video display device 1 (1R · 1L) of the present embodiment developed optically in one direction. In the present embodiment, the configuration is the same as that of the second embodiment except that the light source 11 includes two light source groups 11P and 11Q. That is, also in the present embodiment, the same optical axis adjusting means 15 as that in the second embodiment is provided. In the following, the description will focus on the differences from the second embodiment.

FIG. 22 shows a plan view of the light source 11 in the present embodiment when viewed from the display element 14 side. The light source group 11P of the light source 11 is configured by RGB integrated LEDs having three light emitting portions 11R ₁ , 11G _1, and 11B ₁ that emit light of RGB colors. Similarly, the light source group 11Q is composed of RGB integrated LEDs having three light emitting portions 11R ₂ , 11G _2, and 11B ₂ that emit light of RGB colors. That is, the light source 11 includes two sets of three light emitting units that emit RGB light.

The light emitting units of the light source groups 11P and 11Q are arranged side by side in a direction perpendicular to the incident surface (YZ plane) of the optical axis with respect to the hologram optical element 24. Each color is arranged so as to be plane symmetric. More specifically, the light emitting units 11R ₁ and 11R ₂ are arranged so as to be plane symmetric at positions close to the incident surface, and the light emitting units 11G ₁ and 11G ₂ are plane symmetric with respect to the incident surface outside the X direction. Further, the light emitting portions 11B ₁ and 11B ₂ are arranged on the outer side in the X direction so as to be plane-symmetric with respect to the incident surface. That is, in each light source group 11P * 11Q, each light emission part is arrange | positioned in the order that the wavelength of an emitted light becomes short as it goes to the X direction outer side from the said incident surface side.

In this way, by arranging the light emitting units symmetrically with respect to the incident surface for each color, the light intensity of the emitted light from the _two light emitting units (for example, 11R ₁ and 11R ₂ ) for the same color is added. The center of gravity of the combined total light intensity can be positioned in the symmetry plane (in the incident plane) for each of the RGB colors. That is, the intensity distribution of each color of RGB can be symmetric in the X direction with the symmetry plane as the center. Accordingly, an image with little color unevenness at the center of the optical pupil E can be provided to the observer.

  Note that the plane that is the center of plane symmetry of each light emitting unit may be a plane parallel to the incident plane. In other words, the surface that is the center of symmetry of each light emitting unit may be a surface that is slightly deviated in the X direction from the incident surface. In this case, an image with little color unevenness near the center of the optical pupil E can be provided to the observer.

  By the way, when the light source 11 is composed of two light source groups and the light emitting units are arranged in plane symmetry for each color, the arrangement order of the light emitting units in the direction perpendicular to the incident surface is set to each adjacent group. Vice versa. On the other hand, even when the number of light source groups constituting the light source 11 is an even number of four or more, that is, even when the light source 11 is configured by providing an even number of four or more RGB light emitting units, the above incident If the arrangement order of the light emitting units in the direction perpendicular to the surface is reversed between adjacent pairs, the total light intensity centroid of the light intensity of the emitted light from each light emitting unit is added to the RGB Each color can be positioned in the same plane (including the incident plane) parallel to the incident plane, and an image with little color unevenness at the center of the optical pupil E or in the vicinity thereof can be provided to the observer.

  Therefore, in summary, the light source 11 eventually has two or more even three sets of RGB light-emitting portions, and the arrangement order of the light-emitting portions in the direction perpendicular to the incident plane is as follows. It can be said that an image with little color unevenness can be provided to the observer at the center of the optical pupil E or in the vicinity thereof if the pair is adjacent to each other.

  Further, even if the number of light source groups constituting the light source 11 is an even number of 4 or more, the light emitting units are arranged in plane symmetry with respect to the incident surface and are perpendicular to the incident surface. If the light emitting units located at the same distance from the incident surface on both sides are arranged to emit light of the same color, the center of gravity of the light intensity for each color of the emitted light from each light emitting unit is on the incident surface. Match. Therefore, if the number of light source groups constituting the light source 11 is an even number, by arranging the light emitting units as described above, an image with little color unevenness at the center of the optical pupil can be provided to the observer. It can be said.

  Further, as described above, the hologram optical element 24 is fabricated so as to diffract the image light of each wavelength of 465 ± 5 nm, 521 ± 5 nm, and 634 ± 5 nm at the diffraction efficiency peak and its half-value wavelength width. Thus, since the half-value wavelength width Δλ2 of diffraction efficiency is the same for each color, the longer the wavelength, the greater the angle selectivity (the smaller the incident angle shift with respect to the wavelength change). Therefore, in each light source group 11P and 11Q, each light emission part is arrange | positioned in order that the wavelength of an emitted light becomes short as it goes to an X direction outer side from the optical-axis entrance plane side, Therefore In the optical pupil E The intensity difference between the colors can be reduced, and an image with little color unevenness in the optical pupil E can be provided to the observer. Hereinafter, this point will be described in detail.

Assuming that the wavelength of the diffraction efficiency peak is λ, the refractive index of the medium (interference fringes) of the hologram optical element 24 is n, the thickness of the medium is h, and the incident angle is θ,
λ = 2nhcosθ
The relationship holds. Here, in the B light having a short wavelength and the R light having a long wavelength, when the respective wavelengths are shifted by, for example, the same 5 nm, the rate of change in wavelength is 465/470 for the B light and 634 for the R light. / 639. That is, the rate of change in wavelength is smaller for R light having a longer wavelength than for B light having a shorter wavelength. Therefore, the R light having a longer wavelength is smaller in the incident angle θ with respect to the change in wavelength (the angle selectivity is greater) than the B light having a shorter wavelength. Therefore, when the RGB wavelength width of the light emitted from the light source 11 is the same, the size of the optical pupil diffracted by the hologram optical element 24 is smaller as the wavelength is longer. The optical pupil E includes the entire optical pupil range of each color.

  On the other hand, the intensity of light emitted from the LED (each light emitting unit) of the light source 11 is generally stronger near the center and weaker toward the periphery. Each light emitting unit is arranged so as to be substantially conjugate with the optical pupil in the Y direction, but is diffused by the unidirectional diffusion plate 12 in the X direction and is not conjugate with the optical pupil. However, the position with the strongest intensity in the optical pupil is almost the same as the conjugate position with each light emitting unit when the unidirectional diffuser 12 is not provided.

  Therefore, the pupil center of the long wavelength (R light) with the small optical pupil is positioned on the center side of the optical pupil E, and the pupil center of the short wavelength (B light) with the large optical pupil is positioned outside the center of the optical pupil E. By doing so, the intensity difference depending on the pupil position in the optical pupil E can be reduced for each color. This point will be described in a little more detail.

FIG. 23 is an explanatory diagram showing the relationship between the pupil position in the X direction in the optical pupil E and the light intensity. The light intensity is shown as a relative value for the same color. In addition, the curves indicated by 11R ₁ , 11R ₂ , 11G ₁ , 11G ₂ , 11B ₁ , 11B ₂ in the figure are respectively from the light emitting units 11R ₁ , 11R ₂ , 11G ₁ , 11G ₂ , 11B ₁ , 11B _2. It corresponds to the emitted light.

  As described above, due to the angle selectivity of the hologram optical element 24, the longer the wavelength, the smaller the optical pupil. Therefore, the longer the wavelength, the greater the difference in intensity depending on the pupil position (optical). The intensity difference between the center and the end of the pupil E is large). On the contrary, since the optical pupil E is larger as the wavelength is shorter, the intensity difference depending on the pupil position is smaller as the wavelength is shorter.

  In addition, since the light emitting portion that emits light having a longer wavelength is disposed on the optical axis incident surface side, the position with higher light intensity is closer to the center of the optical pupil E as the light has a longer wavelength. On the contrary, since the light emitting part that emits light having a short wavelength is arranged at a position farther from the optical axis incident surface, the position where the light intensity is high is around the optical pupil E.

  In other words, the longer the wavelength, the greater the difference in intensity depending on the pupil position, but the light emitting units are arranged in such an order that the wavelength of the emitted light becomes shorter from the optical axis incident surface side toward the outside in the X direction. By bringing the position with a high light intensity closer to the center of the optical pupil E, the intensity difference depending on the pupil position, that is, the intensity difference between the center and the end of the optical pupil E can be reduced for light having a long wavelength. As a result, an image with little color unevenness can be provided to the observer over the entire optical pupil E (the pupil center and the periphery of the pupil).

  In addition, the light emitting units of the light source groups 11P and 11Q are arranged in the X direction in the order of wavelengths in which the diffusion in the unidirectional diffusion plate 12 is large (diffuses as the wavelength is shorter), so each color on the optical pupil E The intensity difference is further reduced, and color unevenness can be further reduced. That is, an image with high color purity can be provided to the observer.

  In the above description, an example in which the light source 11 is configured by the light source groups 11P and 11Q in which two sets of RGB light emitting units are provided and each set is an individual package has been described. However, each set has one package. Also good. FIG. 24 shows another configuration example of the light source 11 and shows a plan view when the light source 11 is viewed from the display element 14 side.

As described above, the light source 11 may be configured by a single package of the light emitting units 11R ₁ , 11R ₂ , 11G ₁ , 11G ₂ , 11B _1, and 11B ₂ that emit RGB light. Also in this configuration, by applying the above-described arrangement method of the light emitting units, the intensity difference of each color on the optical pupil E can be reduced and color unevenness can be reduced. Also, as the distance between the light emitting points is closer, RGB colors are more likely to be mixed and a brighter image can be provided. In this respect, the configuration of FIG. 24 in which the distance between the light emitting units can be easily reduced is desirable.

[Embodiment 4]
The following will describe still another embodiment of the present invention with reference to the drawings. In addition, the same member number is attached to the same structure as Embodiment 1 thru | or 3, and the description is abbreviate | omitted.

  FIG. 25 is a cross-sectional view illustrating a schematic configuration of the video display device 1 (1R · 1L) according to the present embodiment. In the video display device 1 of the present embodiment, the light source 11 is configured by a white light source (white LED) that emits white light by exciting a phosphor with blue light or ultraviolet light, and the eyepiece optical system 21 is an eyepiece optical system 51. Except for the replacement, the configuration is exactly the same as in the second embodiment. That is, also in the present embodiment, the same optical axis adjusting means 15 as that in the second embodiment is provided. In the following, the description will focus on the differences from the second embodiment.

  The eyepiece optical system 51 (observation optical system) has a hologram optical element 24 formed on a transparent substrate 52. The substrate 52 is connected to the housing 10 via the support 53. The hologram optical element 24 has an axially asymmetric positive power as in the above-described embodiment, and has a diffraction efficiency peak and a half-value wavelength width of 465 ± 5 nm, 521 ± 5 nm, and 634 ± 5 nm. It is made to diffract the image light. The details of the method for producing the hologram optical element 24 in the present embodiment will be described later.

  In the above configuration, the light emitted from the light source 11 is diffused by the unidirectional diffusion plate 12, condensed in the Y direction by the condenser lens 13, illuminates the display element 14, and modulated by the display element 14. Is done. The image light from the display element 14 is diffracted by the hologram optical element 24 and guided to the optical pupil E. At this time, the hologram optical element 24 is formed larger in the direction perpendicular to the optical axis incident surface than in the direction parallel to the optical axis incident surface, so that the light source 11 and the optical pupil E have a substantially conjugate relationship. Since the optical pupil E is set, the size of the light emitting portion of the light source 11 (for example, x = 3 mm, y = 0.5 mm) is enlarged to 3 times the image magnification of the optical system, and the display element 14 is about 1 As a result of being slightly increased by the diffusion of °, the sizes are x = 10 mm and y = 2.5 mm.

  As described above, in the present embodiment, since a white light source is used as the light source 11, it is not necessary to mix RGB colors, and the light source 11 and the optical pupil E are arranged substantially conjugate to provide a bright image. Is possible.

  Further, since the optical pupil E is larger than the human pupil (about 3 mm) in one direction (X direction), the observer can easily observe the image. Furthermore, in the other direction (Y direction), since the light is focused on the optical pupil E that is almost the same size as the human pupil, a bright image can be provided to the observer without waste.

  Further, in the present embodiment in which the hologram optical element 24 is attached to the substrate 52 to constitute the eyepiece optical system 51, the image light from the display element 14 is directly incident on the hologram optical element 24, so that the hologram optical element 24 is recorded on the hologram optical element 24. The incident angle of light on the interference fringes thus made can be made smaller than that of the configuration of the second embodiment.

  More specifically, in the configuration of the second embodiment, the incident angle of light incident on the hologram optical element 24 is, for example, about 25 ° to 35 ° in the medium. The angle can be, for example, about 10 ° to 15 ° in the medium. Thereby, compared with Embodiment 2, the influence of the wavelength selectivity due to the change in the incident angle is small, and the color misregistration is small. Accordingly, it is possible to display an image with a larger optical pupil E than in Embodiment 2 and with high color purity and a wide color reproduction region.

  In addition, the color reproduction area in the video display device 1 of the present embodiment is an area indicated by a one-dot chain line A2 shown in FIG. It can be seen that this color reproduction region is wider than the broken line A3 and the two-dot chain line A4. Therefore, also in the video display device 1 of this embodiment, the color purity can be increased and the color reproduction region can be expanded.

  Next, a method for producing the hologram optical element 24 in the present embodiment will be described. FIG. 26 is a cross-sectional view showing a schematic configuration of an optical system used for manufacturing the hologram optical element 24 of the present embodiment.

  First, the hologram photosensitive material 24 a is applied on the substrate 52. Here, it is assumed that the hologram photosensitive material 24a is applied on the substrate 52 over a range wider than the irradiation range of the two production light beams. Then, the substrate 52 coated with the hologram photosensitive material 24a is arranged at a predetermined position of the optical system shown in FIG.

  In the optical system, laser light from a light source (not shown) is split into two light beams and converted into point light sources 61 and 71, respectively. Light emitted from the point light source 61 (one of the two production light beams) passes through the diaphragm 62, the manufacturing optical system 63, and the diaphragm 64 in this order to the hologram photosensitive material 24a on the substrate 52 (on the surface side of the substrate 52). Irradiated from the opposite side. By irradiating the hologram photosensitive material 24 a with the emitted light through the manufacturing optical system 63, the hologram optical element 24 to be formed can have positive power that is axisymmetric. In addition, the irradiation range of the said emitted light with respect to the hologram photosensitive material 24a is a range which diffracts only a center light beam among reproduction | regeneration light.

  On the other hand, the light emitted from the point light source 71 is limited in its light beam diameter by the stop 72 and is irradiated on the hologram photosensitive material 24a on the substrate 52 from the back surface side (substrate 52 side). In addition, the irradiation range of the said emitted light with respect to the hologram photosensitive material 24a is a range which diffracts only a center light beam among reproduction | regeneration light.

  By irradiation with these two light beams, interference fringes are recorded in the overlapping portion of the irradiation range of the two light beams on the hologram photosensitive material 24a, and the hologram optical element 24 is manufactured. Thereafter, the eyepiece optical system 51 is completed by performing a baking process and a fixing process.

  In the above optical system, since the numerical apertures (light beam diameters of the emitted light) of the point light sources 61 and 71 are limited by the diaphragms 62, 64, and 72, the two light beams produced on the hologram photosensitive material 24a have the same size. Thus, the hologram optical element 24 can be produced only in the range in which the central light beam having good optical performance is irradiated in the reproduction light. Further, since the two produced light beams interfere with each other in the same range, interference with only one laser beam hardly occurs, and unnecessary interference fringes are not recorded on the hologram photosensitive material 24a. Therefore, the hologram optical element 24 having optically good performance that hardly generates flare and ghost can be produced, and a high-quality image can be provided to the observer.

  Further, since the two light beams used at the time of production are formed by restricting the divergence angles of the light emitted from the corresponding point light sources 61 and 71 by the diaphragms 62, 64, and 72, the hologram optics on the substrate 52 is formed. The size of the element 24 can be easily and reliably controlled at low cost.

  Further, the diameter of the light beam emitted from the point light source 61 is limited by the two stops 62 and 64, but is first limited by the stop 62 to be reflected or diffused at the end of the manufacturing optical system 63 or the like. It is possible to suppress generation of unnecessary light. Then, by restricting the beam diameter of the emitted light by the diaphragm 64, it is possible to suppress unnecessary light such as inter-surface reflection generated in the manufacturing optical system 63 from reaching the hologram photosensitive material 24a.

  Further, the point light source 71 is disposed in the vicinity of the optical pupil E. As described above, by substantially matching the position of the point light source 71 and the position of the optical pupil E when the hologram optical element 24 is manufactured, the video display color can be made the same regardless of the position of the screen. Further, the wavelength of light that is diffracted by the hologram optical element 24 and reaches the optical pupil E during reproduction differs depending on the position of the optical pupil E. However, in the present embodiment, the optical axis adjustment unit 15 performs the optical axis adjustment without changing the position of the optical pupil E with respect to the eyepiece optical system 51, so that the wavelength of light reaching the optical pupil E changes due to the optical axis adjustment. Therefore, the color reproducibility can be kept good.

[Embodiment 5]
The following will describe still another embodiment of the present invention with reference to the drawings. In addition, the same member number is appended to the same structure as Embodiment 1-4. Points that are not mentioned in the first to fourth embodiments will be appropriately described.

  FIG. 27 is a cross-sectional view showing a schematic configuration of the video display device 1 (1R · 1L) according to the present embodiment. The video display device 1 according to the present embodiment includes a light source 11, a unidirectional diffuser 12, a display element 14 ', an optical axis adjusting unit 15, an optical path bending member 17, and a first polarizing plate 18 (polarizer). A second polarizing plate 19 (analyzer), a third polarizing plate 20, and an eyepiece optical system 21. Optical members other than the eyepiece optical system 21 are accommodated in the housing 10, and this housing 10 is supported by a part of the eyepiece optical system 21 (the eyepiece prism 22 in the figure). In the following, the description will focus on the parts that are different from the above-described embodiments.

  The light source 11 is composed of RGB integrated LEDs, and each wavelength of RGB substantially matches the wavelength of light diffracted and reflected by the hologram optical element 24. In the present embodiment, as will be described later, a ferroelectric liquid crystal display element capable of time-division driving is used as the display element 14 ′. Therefore, the light source 11 sequentially emits light corresponding to the three primary colors in time division. Further, since the optical power of the optical path bending member 17 described later is not in the X direction, the light source 11 and the optical pupil E are substantially conjugate in the Y direction.

  The display element 14 ′ is a light modulation element that has a plurality of pixels in a matrix and displays an image by modulating light emitted from the light source 11 for each pixel according to image data. More specifically, the display element 14 'is a reflective ferroelectric liquid crystal display in which a ferroelectric liquid crystal is sandwiched between two substrates, and a reflective film (reflective electrode, pixel electrode) is formed on one substrate side. It is composed of elements. The reflective ferroelectric liquid crystal display element does not have a color filter. Therefore, each pixel of the display element 14 ′ corresponds to each of the three primary color lights sequentially supplied from the light source 11 in a time division manner. It is driven ON / OFF by dividing. Thereby, a color image can be provided to the observer.

  The reflective ferroelectric liquid crystal display element is superior in that it has a wider viewing angle characteristic than a TN (Twisted Nematic) liquid crystal display element, and is incident on the display element 14 ′ from an optical path bending member 17 described later. Even when the incident angle of light is large, an image with high contrast, high color reproducibility (wide color reproduction region), and high display quality can be provided. Further, the degree of freedom of arrangement of each optical element is increased, and a compact and high-performance video display device 1 can be realized.

  Note that the display element 14 ′ may be configured by combining a phase compensation plate and a TN liquid crystal display element to improve viewing angle characteristics. The display element 14 ′ may be a reflective display element that can be time-division driven, and may be constituted by, for example, DMD (Digital Micromirror Device; manufactured by Texas Instruments, USA).

  The optical axis adjusting means 15 has the same function as each embodiment, but in this embodiment, the optical axis adjusting means 15 has a holding frame 15b (holding portion) that holds the substrate of the display element 14 'from the back side. Yes. The holding frame 15b is slidable in a direction intersecting with the optical axis (here, a direction substantially parallel to the display surface of the display element 14 ') and is finally fixed to the housing 10. By adjusting the position of the display element 14 ′ by sliding the holding frame 15b in this manner, the relative positional relationship between the image displayed on the display element 14 ′ and the eyepiece optical system 21 intersects the optical axis. Can change in direction.

  The optical path bending member 17 is a reflection mirror that reflects the light emitted from the light source 11 and guides it to the display element 14 ′, and has a function of bending the optical path from the light source 11 to the display element 14 ′. In the present embodiment, the optical path bending member 17 is configured by a cylindrical concave mirror that collects the light from the light source 11 only in the Y direction, and with respect to the optical path of the light from the display element 14 ′ toward the eyepiece optical system 21. The light source 11 is provided on the opposite side. That is, the optical path bending member 17 is provided at a position where the light path is sandwiched between the light source 11 and the optical path bending member 17.

  The first polarizing plate 18 transmits light in a predetermined polarization direction (here, P-polarized light) out of the light emitted from the light source 11 and guides it to the optical path bending member 17, and the optical path is bent by the optical path bending member 17. Light that is bent and having the same polarization direction as the predetermined polarization direction (here, P-polarized light) is transmitted and guided to the display element 14 '.

  The second polarizing plate 19 transmits light having a polarization direction orthogonal to the light transmitted through the first polarizing plate 18 out of incident light (here, S-polarized light) and guides it to the eyepiece prism 22. In the eyepiece prism 22, the eyepiece prism 22 is attached to the surface on which light from the display element 14 ′ is incident.

  By arranging the second polarizing plate 19 as described above, even if there is unnecessary light (P-polarized light) traveling in the direction from the light source 11 to the eyepiece prism 22, the second polarizing plate 19 ensures that the unnecessary light is transmitted. Therefore, it is possible to reliably prevent ghosts and flares from occurring due to the unnecessary light.

  The third polarizing plate 20 transmits light having the same polarization direction as light transmitted through the first polarizing plate 18 (here, P-polarized light) out of the light emitted from the light source 11 to the optical path bending member 17. It is a guide. The third polarizing plate 20 is disposed on the light source 11 side (between the optical path and the light source 11) with respect to the optical path of light traveling from the display element 14 'to the eyepiece optical system 21.

  By disposing such third polarizing plate 20, the light in the polarization direction (S-polarized light) that can be transmitted through the second polarizing plate 19 among the light emitted from the light source 11 is converted to the third polarizing plate 20. Can be cut in advance. That is, by arranging the third polarizing plate 20, the S-polarized light reaches the eyepiece optical system 21 directly from the light source 11, or is reflected by the surface of the first polarizing plate 18 and reaches the eyepiece optical system 21. There is nothing. Thereby, it is possible to prevent the occurrence of ghost (flare) due to such light, and it is possible to reliably avoid the deterioration of the image quality.

  In the above configuration, when each color light of RGB is emitted from the light source 11 in a time-sharing manner, each color light (for example, P-polarized light) is first transmitted through the third polarizing plate 20, and then the first polarizing plate 18 and the first polarizing plate 18. The light passes through the direction diffusion plate 12 and is reflected by the optical path bending member 17. Then, the light (P-polarized light) reflected by the optical path bending member 17 passes through the unidirectional diffusion plate 12 and the first polarizing plate 18 again and enters the display element 14 ′.

  In the display element 14 ′, incident light is reflected, but at that time, the light is modulated in accordance with image data for each RGB, and is emitted from the display element 14 ′ as polarized light (S-polarized light) different from the incident light. At this time, video corresponding to the image data is displayed on the display element 14 ′ for each RGB in a time division manner. Light emitted from the display element 14 ′ (image light for each RGB) crosses the optical path from the light source 11 to the optical path bending member 17 and reaches the eyepiece optical system 21, passes through the second polarizing plate 19, and is eyepiece. The light enters the prism 22.

  In the eyepiece prism 22, the incident image light is totally reflected a plurality of times by two opposing planes of the eyepiece prism 22, guided to the hologram optical element 24 disposed at the lower end of the eyepiece prism 22, reflected there, and reflected by the optical pupil E. To reach. Accordingly, at the position of the optical pupil E, the observer can observe an enlarged virtual image of each RGB image displayed on the display element 14 ′ as a color image.

  On the other hand, the eyepiece prism 22, the deflection prism 23, and the hologram optical element 24 transmit almost all the light from the outside, so that the observer can observe the outside world image with see-through. The virtual image of the image displayed on the display element 14 ′ is observed so as to overlap with a part of the external image.

  As described above, also in the video display device of the present embodiment, since the optical axis adjustment means 15 is provided, it is possible to avoid a decrease in luminance and image quality of the observation video at the position of the optical pupil E due to the optical axis adjustment. Can do.

  In addition, in the reflective display element 14 ′, a semiconductor such as silicon can be used as a substrate, so that a small and highly integrated display element can be manufactured. In addition, since a peripheral circuit including a switching element (for example, TFT) and wiring for turning on / off each pixel can be disposed on the substrate on the side opposite to the display side, the aperture ratio can be easily improved. And bright images can be displayed.

  Further, since the ferroelectric liquid crystal display element has a merit that the driving speed is high, therefore, the above-described time-division driving method is adopted by configuring the display element 14 ′ with a reflective ferroelectric liquid crystal display element. be able to.

  Here, a conventional color filter system that displays a color image with RGB light transmitted through the color filter is a space in which a white light source is always turned on and any one of RGB color filters is arranged in one pixel to perform color display. Since it is a split drive system, it requires three times as many pixels as in the case of monochrome display. In addition, when image light of an unnecessary color is shielded, it is necessary to shield each pixel while keeping the light source on. Since it is difficult to completely shield the light from each pixel, the color filter method has low color purity of a single color.

  On the other hand, in the time-division driving method, each light emitting portion of RGB is sequentially turned on by the light source, and thus, for example, when displaying a single color, the remaining two light emitting portions are turned off. Thereby, an image with high color purity and high contrast can be displayed. Further, since the display element 14 ′ that employs the time-division driving method does not have a color filter, it has a high light transmittance and can display a bright image.

  Further, since the reflective display element 14 has a high aperture ratio as described above, there is little diffusion of light when passing through each pixel. Therefore, the light source 11 and the optical pupil E can be reliably made substantially conjugate in the Y direction.

[Embodiment 6]
The following will describe still another embodiment of the present invention with reference to the drawings. In addition, the same member number is attached to the same structure as Embodiment 1 thru | or 5, and the description is abbreviate | omitted. In the present embodiment, a head mounted display (hereinafter also referred to as HMD) to which the video display device of each of the above embodiments is applied will be described.

  FIG. 28A is a plan view showing a schematic configuration of the HMD according to the present embodiment, FIG. 28B is a side view of the HMD, and FIG. 28C is a front view of the HMD. is there. The HMD has two video display devices 1R and 1L arranged in front of the observer's right eye and in front of the left eye, and support means 2 for supporting them.

  The video display devices 1R and 1L allow an observer to observe an external image as a see-through, display an image, and provide it to a viewer as a virtual image, and adopt the configuration described in each of the above-described embodiments. Can do. In the video display devices 1R and 1L shown in FIG. 28C, portions corresponding to the right eye lens and the left eye lens of the spectacles are configured by bonding the eyepiece prism 22 and the deflection prism 23 together.

  The support means 2 supports the video display devices 1R and 1L in front of the right and left eyes of the observer, and includes a bridge 3, a frame 4, a temple 5, a nose pad 6, and a cable 7. And an external light transmittance control means 8. The nose pad 6 and the external light transmittance control means 8 are supported by the bridge 3. The frame 4, the temple 5 and the nose pad 6 are provided as a pair on the left and right sides. However, when these are distinguished from each other, the right frame 4R, the left frame 4L, the right temple 5R, the left temple 5L, and the right nose pad 6R. The left nose pad 6L is expressed.

  The video display devices 1R and 1L are connected by a bridge 3. The right temple 5R is rotatably supported by the right frame 4R, and is connected to the opposite side of the connection side between the video display device 1R and the bridge 3 via the right frame 4R. Similarly, the left temple 5L is rotatably supported by the left frame 4L, and is connected on the opposite side to the connection side between the video display device 1L and the bridge 3 via the left frame 4L.

  The cable 7 is a wiring for supplying an external signal (for example, a video signal, a control signal) and electric power to the video display devices 1R and 1L, and is provided along the right temple 5R, the right frame 4R, and the bridge 3. The external light transmittance control means 8 is provided to control the transmittance of external light (light of an external image), and is located in front of the video display devices 1R and 1L (on the side opposite to the observer). ing.

  When the observer uses the HMD, the right temple 5R and the left temple 5L are brought into contact with the right and left heads of the observer, and the nose pad 6 is put on the nose of the observer so as to wear general glasses. The HMD is attached to the observer's head. In this state, when the video is displayed on the video display devices 1R and 1L, the observer can observe each display video of the video display devices 1R and 1L as a virtual image with both eyes, and the video display devices 1R and 1L can be viewed. Thus, it is possible to observe the outside world image with see-through.

  At this time, if the external light transmittance control means 8 sets the external light transmittance to be low, for example, 50% or less, it becomes easier for the observer to observe the image on the image display devices 1R and 1L. If the light transmittance is set to be high, for example, 50% or more, the observer can easily observe the external image. Therefore, the external light transmittance in the external light transmittance control means 8 may be set as appropriate in consideration of the ease of observation of the video and external images of the video display devices 1R and 1L.

  As described above, the HMD of the present embodiment includes the video display devices 1R and 1L and the support means 2 that supports the video display devices 1R and 1L in front of the observer's eyes. Since 1L is supported by the support means 2, the observer can observe the images provided from the image display devices 1R and 1L in a hands-free manner.

  In this embodiment, the example in which the video display devices 1R and 1L are applied to the HMD has been described. However, for example, the video display devices 1R and 1L may be applied to a head-up display.

  Of course, it is possible to configure the video display device and the HMD by appropriately combining the configurations and methods described in the embodiments.

  The video display device of the present invention can be used for a head-up display or a head-mounted display, for example.

FIG. 3 is an explanatory diagram showing an expanded optical path of light emitted from the center of a display area of a display element in each of the right-eye and left-eye video display devices according to an embodiment of the present invention. It is explanatory drawing which expand | deploys and shows the optical path of the light radiate | emitted from the light source of each said video display apparatus. In other structural examples of each said video display apparatus, it is explanatory drawing which expand | deploys and shows the optical path of the light radiate | emitted from the center of the display area of a display element. It is explanatory drawing which expand | deploys and shows the optical path of the light radiate | emitted from the light source of each video display apparatus of the said structure. FIG. 11 is an explanatory diagram showing an expanded optical path of light emitted from the center of a display area of a display element in still another configuration example of each of the video display devices. It is explanatory drawing which expand | deploys and shows the optical path of the light radiate | emitted from the light source of each video display apparatus of the said structure. FIG. 11 is an explanatory diagram showing an expanded optical path of light emitted from the center of a display area of a display element in still another configuration example of each of the video display devices. It is explanatory drawing which expand | deploys and shows the optical path of the light radiate | emitted from the light source of each video display apparatus of the said structure. It is sectional drawing which shows the structure of the outline of the video display apparatus concerning other embodiment of this invention. It is explanatory drawing which optically expands and shows the optical path in the said video display apparatus in one direction. It is a graph which shows the radiation characteristic of LED used as a light source of the said video display apparatus. It is a graph which shows the diffusion characteristic of the one way diffusion plate of the said video display apparatus. It is explanatory drawing which shows distribution of the optical intensity of a certain wavelength in the position of the optical pupil before an optical axis adjustment. It is sectional drawing which shows the structure of the outline of the optical system used for preparation of the hologram optical element of the said video display apparatus. It is explanatory drawing which shows the spectral intensity characteristic of the said light source. It is explanatory drawing which shows the wavelength dependence of the diffraction efficiency in the said hologram optical element. It is explanatory drawing which shows the color reproduction area | region of the virtual image represented using the XY chromaticity coordinate in an XYZ color system. It is explanatory drawing which shows the relationship between the pupil position in an optical pupil, and the main diffraction wavelength. FIG. 11 is an explanatory diagram showing an expanded optical path of light emitted from the center of a display area of a display element of each video display device in another configuration example of the video display device. It is explanatory drawing which expand | deploys and shows the optical path of the light radiate | emitted from the light source of each video display apparatus of the said structure. It is explanatory drawing which optically expands and shows the optical path in the video display apparatus based on further another embodiment of this invention in one direction. It is a top view when the light source of the said video display apparatus is seen from the display element side. It is explanatory drawing which shows the relationship between the pupil position of the X direction in an optical pupil, and light intensity. While showing the other structural example of the said light source, it is a top view when the light source is seen from the display element side. It is sectional drawing which shows the structure of the outline of the video display apparatus based on further another embodiment of this invention. It is sectional drawing which shows the structure of the outline of the optical system used for preparation of the hologram optical element of the said video display apparatus. It is sectional drawing which shows the structure of the outline of the video display apparatus based on further another embodiment of this invention. (A) is a top view which shows the schematic structure of HMD which concerns on further another embodiment of this invention, (b) is a side view of HMD, (c) is a front view of HMD. is there. In the conventional video display apparatus, it is explanatory drawing which shows typically the structure of one schematic of the left and right optical systems.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image display element 1R Image display element 1L Image display element 2 Support means 11 Light source 13 Condensing lens (illumination optical system)
DESCRIPTION OF SYMBOLS 14 Display element 14 'Display element 15 Optical axis adjustment means 16 Light source position adjustment mechanism 21 Eyepiece optical system (observation optical system)
22 Eyepiece prism (first transparent substrate)
23 Deflection prism (second transparent substrate)
24 Hologram optical element 51 Eyepiece optical system (observation optical system)
E Optical pupil

Claims (19)

A pair of left and right light sources;
A pair of left and right display elements that modulate the light from each light source and display an image;
A pair of left and right observation optical systems for guiding the light of the image displayed on each display element to the pair of left and right optical pupils, and
An optical axis that adjusts the angle formed by the pair of left and right optical axes by changing the relative positional relationship between the image displayed on the display element and the observation optical system in a direction intersecting the optical axis for at least one of the left and right Adjusting means,
In each of the left and right, the light source is arranged substantially conjugate with the optical pupil,
The image display apparatus according to claim 1, wherein the optical axis adjusting means changes the positional relationship without changing the position of the optical pupil with respect to the observation optical system.   The video display device according to claim 1, wherein the optical axis adjustment unit changes the positional relationship by adjusting a position of a display element with respect to the observation optical system.   The video display device according to claim 1, further comprising a pair of left and right illumination optical systems that collect light from the light source and guide the light to the display element.   The video display device according to claim 1, wherein the light source is an LED.   5. The video display device according to claim 1, wherein the light source emits light having a plurality of wavelengths having a light intensity peak. In each of the left and right, the observation optical system includes a volume phase type reflection type hologram optical element,
6. The image display device according to claim 1, wherein the hologram optical element guides the image light from the display element to the optical pupil by diffracting and reflecting the image light.   The video display apparatus according to claim 6, further comprising a pair of left and right light source position adjusting mechanisms that change the position of the optical pupil by adjusting the position of the light source.   8. The image display device according to claim 6, wherein the hologram optical element has an axially asymmetric positive optical power.   9. The video display device according to claim 8, wherein the optical pupil is larger in a direction perpendicular to the incident surface than in a direction parallel to the incident surface of the optical axis to the hologram optical element.   The video display device according to claim 9, wherein the light source and the optical pupil are substantially conjugate in a direction parallel to the incident surface. The light source has three light emitting units that emit light corresponding to the three primary colors,
The video display device according to claim 9, wherein the light emitting units are arranged side by side in a direction perpendicular to the incident surface. The light source has an even number of three light emitting units that emit light corresponding to the three primary colors,
12. The arrangement according to claim 6, wherein the arrangement order of the light emitting portions in the direction perpendicular to the plane of incidence of the optical axis on the hologram optical element is reversed between adjacent groups. The video display device described in 1. The light source has an even number of three light emitting parts,
Each light emitting unit is arranged symmetrically with respect to the incident surface, and light emitting units located at the same distance from the incident surface on both sides in a direction perpendicular to the incident surface emit light of the same color. The video display device according to claim 11, wherein the video display device is arranged as described above. The light source has two sets of three light emitting parts,
The light emitting units of each set are arranged in an order such that the wavelength of the emitted light becomes shorter from the incident surface side toward the outer side in the direction perpendicular to the incident surface. Video display device.   15. The image display device according to claim 6, wherein the hologram optical element is a combiner that guides image light from the display element and external light simultaneously to the observer's pupil.   16. The video display device according to claim 15, wherein the half-value wavelength width of the diffraction efficiency peak of the hologram optical element is 5 nm or more and 10 nm or less.   The observation optical system includes a first transparent substrate that totally reflects the image light from the display element and guides the light to the observer's pupil while transmitting the external light to the observer's pupil. The video display device according to claim 1, wherein the video display device is a video display device.   The video display apparatus according to claim 17, wherein the observation optical system includes a second transparent substrate for canceling refraction of external light on the first transparent substrate. A video display device according to any one of claims 1 to 18,
A head-mounted display comprising support means for supporting the video display device in front of an observer's eyes.

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